1. Field of the Invention
The present invention pertains broadly to control of atmospheric conditions within an enclosed space, and move particularly to detection of hygienically offensive and/or hazardous atmospheric conditions within an enclosed work place, and rapid evacuation of the offensive or hazardous atmosphere and replacement with atmosphere of suitable quality. Potentially offensive or hazardous conditions are detected and corrective measures are implemented so as to maintain the enclosed atmosphere within predetermined hygienic parameters.
2. Description of the Prior Art
Until recently industrial-type buildings, that is, large buildings having a generally open interior within which manufacturing processes are carried on, were generally heated from a central heating plant, with ducts or pipes delivering heated air, steam or a suitable liquid from the heating plant as a heat carrying medium for distributing heat to various areas of the building. Cooling, if it was available, was likewise provided by delivering cooled air from a central unit through duct work to specific discharge areas. More than likely, any attempt at cooling involved merely opening doors and windows to allow random fresh air circulation, perhaps augmented by the use of numerous exhaust fans and fans directing air toward workers. Air quality was not deemed of great significance, and if working conditions became intolerable, an attempt was made to extract stale or polluted air by means of exhaust fans through vents in the roof or side walls. There was little or no correlation between the heating or cooling and the ventilation, and no monitoring to assure that air quality was maintained within environmentally and hygienically safe predetermined parameters.
More recently, direct-fired space heating units have come into use for heating relatively large industrial type buildings. Such units are generally disposed exteriorly of the building as on the roof or along the side walls, and include a cabinet housing a burner and a fan. The fan draws fresh air from the outside, as well as return air from the interior of the building. During periods when heat is required for the building, a portion of the fresh air is drawn over the burner to be heated, and the remaining fresh air is mixed with recirculated building air in selected proportions. The heated and unheated air are combined downstream from the burner and discharged into the building to maintain the building interior at a desired temperature and pressure. Where cooling is to be provided for the building, an appropriate heat exchange unit may likewise be provided in association with the cabinet for conditioning the air prior to discharge into the building.
Such units purportedly maintain temperature and pressure at desired levels by altering, on demand, the complementary proportions of outside air and recirculated building air passing through the unit or units for discharge into the building. No duct work is employed, and once the air is discharged into the building its movement is randomly influenced by various factors such as building infiltration, exfiltration, convection currents, heat producing activities in various areas of the building, outside wind direction and velocity, air density differentials, and ventilation systems. Thus, while the space heating or air handling units themselves may function as intended, their operation often results in objectionable and uncontrollable hot or cold areas within the building. They also are not effective in removing airborne pollutants and contaminants or controlling humidity in localized areas of the building so as to maintain air quality throughout the building within current environmentally acceptable standards.
In order to overcome these shortcomings of the prior art, a system for regulation of atmospheric conditions within a confined space has been devised as described in commonly assigned U.S. Pat. Nos. 4,850,264 and 4,960,041, the disclosures of which are herein incorporated by reference. In accordance with the inventions as fully described in the aforementioned patents, a so-called global control concept is utilized wherein the building interior defines an essentially enclosed system, with sufficient outside air being admitted through air handling units positioned about the building to continuously maintain the interior of the building under a slight positive pressure throughout relative to outside atmospheric pressure. Controllable vents are provided at strategic locations around the perimeter of the building, and sensing units are located throughout the building interior to monitor atmospheric conditions such as temperature, humidity and the level of particulates and pollutants. The sensing units or monitoring stations generate signals indicative of the readings for transmittal to a central computer. The central computer periodically monitors the signals from each sensing unit and compares them to stored data representing desired parameters for the atmospheric conditions in the various zones monitored by the sensors. Signals are generated in response to noted deviations from the prescribed parameters, and the signals are utilized to regulate the controllable vents and the air handling units so as to modify the incoming air and/or cause air to be expelled through an appropriate vent or vents in the area of the monitoring station or stations until atmospheric conditions again fall within the prescribed parameters. Operation of the various air handling units and vents is correlated so that air delivered from the air handling units migrates to specified areas in a controlled manner without the use of duct work to restore and/or maintain atmospheric conditions throughout the building within the prescribed parameters.
The aforedescribed system has been found extremely effective in maintaining atmospheric conditions within desired parameters in most facilities. However, in certain facilities housing production operations which periodically generate and emit abnormally high amounts of airborne contaminants, it has been found that the capability to quickly provide, on demand, accelerated evacuation of such contaminants from particular areas would be highly advantageous. By way of example, such facilities might include those which house foundry activities, welding areas, rubber vulcanizing operations and the like.